In cameras employing a 35 mm. cinefilm, the film is usually wound successively with advancement of photographing operation, without using any light-blocking or liner paper, around a spool disposed in the camera body which is itself in a light-blocked state. Then, at the time when a predetermined number of film frames have been exposed, the film is rewound into a patrone or magazine from which the light is also blocked. Thus, the film is not taken out of the camera body in the state where it is wound around the spool, but is only taken out after it has been rewound into the patrone or magazine. Accordingly, even if the film is wound around the spool loosely without imparting a proper tension to it, there is no danger of light leakage encountered.
While in cameras employing a roll film, or for example a 60 mm. roll film (usually referred to as 120 or 220 type), wherein the light-blocking or liner paper including the leader portion is superposed on the film and wound together with the film for blocking the light, the film which is wound as the photographing operation proceeds is not rewound but, rather, is taken directly out of the camera in the wound state. Therefore, to eliminate the danger of light leakage and accidental exposure, film of this type has to be wound accurately and in a tightly tensioned state.
If the film is wound loosely or partially engaged in an offset position, with the flanges formed on the opposite ends of the spool, external light will intrude through the gap defined between the liner paper and film. To eliminate this danger, the width of the liner paper including the leader portion is selected so as to have a slightly larger size than the interspace between the opposite flanges on the spool, and the width of the film is selected so as to have a slightly smaller size than said interspace. In this way, when wound around the spool shaft, the liner paper will be engaged at its opposite side edges with the flanges and slightly bent upwardly. Because of the slight difference between the width of the liner paper and the interflange space of the spool, it is essential in winding the film to rotate the spool precisely around the central axis of the spool and, in addition, to make the leader portion of the liner paper engaged with the spool in a controlled direction which is precisely identical with the winding direction.
To wind the film precisely around the spool, in spite of the slight difference between the width of the liner paper and the interflange space of the spool, the film has to be wound while a sufficient tension is being applied against the winding resistance. In a practical operation, it has been required heretofore to apply a sufficiently large force to the film.
The foregoing problems are eliminated by the subject invention. More particularly, the dangers of the roll film of the foregoing type being wound loosely and the film and liner paper being wound together around the spool in an offset position and engaged with one of the opposite spool flanges, which happens when the film is wound in the out-of-perpendicular direction to the axis of rotation of the spool shaft, are eliminated. In this way, the invention makes it possible to eliminate the danger of light leakage when the rear lid of the camera is opened and the wound film is taken out. Further, failure in the photographing operation which might otherwise be encountered, due to improper film winding, is avoided.
In accordance with the present invention, a tension number is arranged between the winding spool shaft on which the winding spool is mounted and a support member or roller adapted to guide the film together with the liner paper to the winding spool. The tension member pushes the film from outside the plane, including the common tangential line connecting the outer circumferences of the support member or roller and spool shaft toward the plane. The tension member may preferably be in the form of a roller having opposite end portions, each of these end portions having an increasingly larger diameter toward the outer end thereof.